At the 2002 IA Summit, while talking about New Roles in Information Architecture, I showed the number of Google Hits for a handful of related search terms.
Since then, it's been interesting to periodically review the annual growth rates of these user experience memes, and fun to explore the questions they raise.
For instance, why is usability continuing to outpace information architecture and user experience? And why is findability the fastest growing meme on the list?
You should've included folksonomy, which went from 0 hits in August 2004 to 1.6 million today (and would be zinging by findability as the fastest growing meme on the list ;).
I didn't include folksonomy on my list because it's not a real word.
And, in case you're wondering, I'm just kidding.
Perhaps I should have called my book Ambient Folksonomies.
This may be a bit off topic, but the growing interest in these various areas has sprung a wide variety of job titles -- though they are all similar or identical as far as their roles: User Experience Designer, Interaction Designer, Interface Designer, Experience Architect, on and on. Though I'm excited about the growth in this area, it sure makes it hard knowing what terms to enter when searching for a job!
In most of the web stuff I've published on IA, the term I'm using most often is "IA" ...
Unfortunately, there's no reliable way measure instances of IA in the meme-0-sphere which mean Information Architecture. There're likely many other IAs in the stew...
Somewhat related is the growth in non-English terminology:
http://blog.vanderbeeken.com/2005/12/experience_desi.html